In the field of offshore oil and/or gas production, pipeline systems may be used. For example, at offshore oilfields, subsea pipelines are used to transport the multiphase mixture of oil, gas and water from producing wells to the processing facilities on the land. Several kilometers of pipeline run on the seabed for this purpose.
Pipelines may be provided with a heating system. The oil and or gas products inside the pipeline may exit from a well at a high temperature and pressure, but are kept warm along the pipeline in order to avoid the formation of plugs. This may become critical particularly during production shut-downs. Considering that a length of a pipeline may be in the order of several kilometers, the electrical current passing through the heating system may be high and the magnetic field generated is proportional to the current.
One known heating system is Direct Electrical Heating (DEH), based on the use of the metallic pipeline as one thermal conductor and a cable (e.g., a “piggyback” cable) connected to the metallic pipeline and used as another thermal conductor.
The pipeline is provided with a coating for isolating the pipeline from the contact with sea water (e.g., in order to prevent corrosion). Additionally, the coating also helps in preventing heating power from the heating system to be lost to the external environment.
Along the pipeline, a plurality of sensors may be installed for remotely monitoring the conditions of the pipeline itself and may promptly detect any damage or problem. The sensors communicate measured values to a pipeline monitor and control center that may either be onshore or offshore. For example, PH sensors may be provided for indirect measurement of corrosion or pressure sensors may be provided for monitoring any excessive pressure drop along the pipeline that may be due to a leak. Mass flow rate sensors may also be installed for detecting leaks. Ultra sound transducers may also be used for corrosion measurements and strain gauge sensors may be used for displacement measurements along the pipeline.
The main drawback of such a layout structure is that transferring data from the sensors to the control center is so disturbed as to be practically muted by the electromagnetic field generated by the heating system.